The present invention relates to intubation and, more particularly, to a system and method for performing endotracheal intubation and adjusting endotracheal tube cuff filling.
In the medical treatment of patients requiring breathing assistance, it is common to insert an endotracheal tube into the trachea of the patient, by way of the mouth, nose or any other surgically created opening. One end of the endotracheal tube is connected to a ventilator which periodically forces air into the lungs through the tube. The inner end of the tube is typically provided with an inflatable cuff which is inflated by conventional means subsequently to the insertion of the tube into the trachea. The inflated cuff is supposed to provides a seal against the interior wall of the trachea.
In such cuffed endotracheal tubes, if the cuff is brought into contact with the inner wall of the trachea under too high pressure, normal blood flow in the mucosa is disturbed due to excess pressure for capillary vessels at the contact portion, resulting in tissue ischemia or inadequate blood flow. Prolonged ischemia can cause varying degrees of injury, such as erosion of the mucosa, destruction of the tracheal cartilage rings, or segmental tracheomalacia with dilation of the trachea. Even more dramatic is full thickness erosion which may result in perforation of the innominate artery anteriorly or perforation of the esophagus posteriorly. Patients requiring long term ventilatory support oftentimes developed late complications of tracheal stenosis, from mild to incapacitating obstruction.
On the other hand, if the cuff is brought into contact with the inner wall of the trachea under too low a pressure, the artificial respiration can be inhibited due to a leakage of anesthetic gas, oxygen or air. Furthermore, when the pressure is low, bodily secretions, mucous or other unwanted fluids can pass progressively between the inner surface of the trachea and the outer surface of the cuff. These secretions can pass from the trachea and enter the bronchi, potentially to cause lung infections.
It is therefore necessary to maintain the cuff contact pressure on the inner wall of the trachea at an appropriate level so as to prevent the leakage of air from between the inflated cuff and the tracheal wall during mechanical ventilation, while at the same time maintaining the necessary blood flow in the capillaries at the contact portion.
To prevent tissue damage caused by prolonged pressure from the cuff, the physician periodically deflates and re-inflates the cuff. However, this procedure is rarely done frequently enough or for a long enough period of time to allow adequate reperfusion of the tissue. Therefore, this procedure does not dependably prevent tracheal wall ischemia.
A variety of endotracheal tubes have been developed. For example, U.S. Pat. No. 4,159,722 discloses an improved pressure regulator for an inflatable cuff on an endotracheal tube which prevents relatively rapid pressure increases and permits relatively slow pressure increases. The pressure regulator provides a visual indication of the air pressure in the cuff.
U.S. Pat. No. 4,305,392 attempts to solve the problem of secretion leakage by suctioning. The endotracheal tube is combined with a suction device in a form of a chamber with suction ports for suctioning out fluids in the trachea above the cuff and for introducing medicinal fluids into the trachea.
U.S. Pat. No. 4,501,273 attempts to solve the problem of leakage by controlling the cuff. The pressure within the cuff automatically increases in proportion with the increases in pressure fed to the interior of the endotracheal tube, thereby preventing breakdown or leakage in the seal between the inflated cuff and the trachea wall.
U.S. Pat. No. 5,765,559 addresses the issue of constant static pressure exerted by the cuff on the tracheal wall which, during prolonged surgery, may result in tracheal stenosis. The proposed solution includes a cuffed endotracheal tube having a plurality of cuff rings, each being capable of inflating and deflating periodically such that when one or more of the cuff rings deflate the others remains inflated. This reduces damage to the tracheal wall due to constant pressure on fixed locations.
None of the above and other prior art technologies, however, monitor leakage at the contact area between the cuff and the tracheal inner wall.
A different approach is disclosed in International Patent Application, Publication No. WO 2002/076279 and U.S. Pat. No. 6,843,250 both filed by the Inventor of the present invention. In this approach, the concentration of carbon dioxide is monitored in the patient's airway between the cuff and the vocal cords. Based on the monitoring, the inflation of the cuff is adjusted so as to prevent the leakage of carbon dioxide past the cuff. The inflation of the cuff is adjusted to provide a minimum inflation pressure, which prevents leakage of carbon dioxide past the cuff.
Additional prior arts of relevance include U.S. Pat. Nos. 3,504,676, 3,794,036, 4,305,392, 4,770,170, 4,825,862, 5,067,497, 5,579,762, 5,582,166, 5,582,167, 5,752,921, 5,819,723, 5,937,861 and 6,062,223.
The present invention provides solutions to the problems associated with prior art endotracheal intubation techniques.